When a folder is being imported into LR6 from the desktop, the files are being renamed automatically even though no such action is being prompted in any dialog box.
Then the new #'s are completely different from the original capture #'s.
Lightroom will not rename files unless you tell it to.
Precisely how are you importing? Via the Synchronize command, or File Import? If Synchronize, make sure you display the Import dialog and review the renaming settings. In the Import dialog, are you choosing Copy, Move, or Add? Again, review the renaming settings.